CY7C656xx
Document Number: 38-08037 Rev. *M
Page 5 of 25
Port Indicators
The USB 2.0 port indicators are also supported directly by
CY7C656xx. According to the specification, each downstream
port of the hub optionally supports a status indicator. The
presence of indicators for downstream facing ports is specified
by bit 7 of the wHubCharacteristics field of the hub class
descriptor. The default CY7C656xx descriptor specifies that port
indicators are supported (wHubCharacteristics, bit 7 is set). If
port indicators are not included in the hub, disable this bit through
EEPROM settings.
Each port indicator pin is strategically located directly on the
opposite edge of the port with which it is associated. A port
indicator provides two colors: green and amber. This is usually
implemented as two separate LEDs, one amber and the other
green. A combination of hardware and software control is used
to inform the user of the current status of the port or the device
attached to the port and to guide the user through problem
resolution. Colors and blinking provide information to the user.
The significance of the color of the LED depends on the opera-
tional mode of CY7C656xx. The CY7C656xx port indicators has
two modes of operation: automatic and manual.
On power up the CY7C656xx defaults to automatic mode, where
the color of the Port Indicator (green, amber, off) indicates the
functional status of the CY7C656xx port. In automatic mode, the
CY7C656xx turns on the green LED whenever the port is
enabled and the amber LED when an overcurrent condition is
detected. The color of the port indicator is set by the port state
machine. Blinking of the LEDs is not supported in automatic
mode. Table 1 identifies the mapping of color to port state in
automatic mode.
The LED control lines can also be modulated with a square wave
for power conservation. The polarity of these pins is program-
mable, see on page 13.
In manual mode, the indicators are under the control of the host,
which can turn on the LEDs, or leave them off. This is done by a
USB Hub class request. Blinking of the LEDs is supported in
manual mode. The port indicators enable the user to intervene
in any error detection. For example, when babble is detected
while plugging in a defective device, or when an overcurrent
condition occurs, the port indicators corresponding to the
downstream port blink green or only light the amber LED, respec-
tively.
Table 2 displays the color definition of the indicators when
CY7C656xx is in manual mode.[1]
Table 1. Automatic Port State to Port Indicator Color Mapping
Downstream Facing Hub Port State
Powered Off
Disconnected, Disabled,
Not Configured, Resetting, Testing
Enabled, Transmit, or
TransmitR
Suspended, Resuming,
SendEOR, Restart_E/S
Off or Amber, if due to an
overcurrent condition
Off
Green
Off
Table 2. Port Indicator Color Definitions in Manual Mode
Color Definition
Port State
Off
Not operational
Amber
Error condition
Green
Fully operational
Blinking Off/Green
Software attention
Blinking Off/Amber
Hardware attention
Blinking Green/Amber
Reserved
Note
1. Information presented in Table 1 and Table 2 is from USB 2.0 specification Tables 11-6 and 11-7, respectively.
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